Liliana, Deathmage's Cry

+8: This ability can only be used if you've cast another spell with "Liliana" in its name and you've casted at least 2 zombies this turn.
-16: Create 7 2/2 black zombies with trample and "This creature can't block and can attack once every other turn."
-20: Destroy target creature. If you controlled that creature target opponent loses 10 life. If they can't you win the game.